Editing With Ed
| Field | Unix System Administration |
| Went Obsolete | early 1990s |
| Made Obsolete By | More robust text editors (vi, emacs, joe, pico, etc…) |
| Knowledge Assumed | The ability to edit text line-by-line with no help or context sensitivity |
| When useful | When a system was severely broken an no other editor was available |
Ed(1) is one of the oldest and most basic text editors that could be found on any Unix or Unix derivative system and is still found in just about every Unix/BSD/Linux implementation. The DOS text editor edlin is a close relative. ed(1) evolved into ex(1), which evolved into vi(1). There was no full-screen view of the text as there is in more robust editors (see list above). All edits were made line-by-line, with no context sensitivity or online help. In particular, ed(1) will reply with '?' to all the following commands: help, ?, quit and exit.
Despite these shortcomings, ed(1) is one of those tools that will likely continue to occupy a place in many old-school sysadmins' emergency toolkits. Because of its limited functionality, ed typically has a very small resource footprint which made it well suited to cases when a machine had limited resources or was crippled and the sysadmin needed a way to get it back online. In addition, ed(1) has the option -s which makes it possible to run it within a script; this is rarely used but unavoidable in some cases.
Wikipedia reference here: http://en.wikipedia.org/wiki/Ed_%28text_editor%29
